Water shortage and associated changes in organic nitrogen betweenPappophorum caespitosum(Gramineae) provenances

Three provenances ofPappophorum caespitosum, a forage native grass from the temperate arid region of Argentina, were studied to gain a physiological knowledge of the seasonal organic N status in response to adequate water supply and water stress conditions; and to assess the extent to which variations in the N status between these provenances arise under different water regimes. Plant part samples were analysed for free and bound organic N fractions. Water shortage resulted in a significant depression of plant growth in all provenances. Total N concentration declined along the annual cycle in both water treatments, but it was higher under water stress. The size of the free N pool was very large, suggesting that it may act like an osmoticum. Nitrogen use efficiency increases along the growing period, while the rate of N intake and the specific leaf N content decrease. Variability was found between provenances in most of the physiological and biochemical traits examined under both water regimes.     

The coupled rotation of the inner core

The rotation of the inner core (IC) is influenced by the rest of the Earth through a number of coupling mechanisms. Among four possible coupling mechanisms, gravitational, pressure, viscous and electromagnetic, the first two torques are dominant. Numerous existing IC gravitational torque estimates have been shown to agree very well with one another Xu & Szeto 1996 ). It is shown in this paper that different estimates of the IC pressure torque are also in good agreement.
The coupled rotation of the IC has been investigated in the frequency domain by several research groups (Mathews et al. 1991a,b; De Vries & Wahr 1991 ; Dehant et al. 1993; Jiang 1993 ). Not all of these efforts obtained two IC-related rotational modes, the inner-core wobble (ICW) and the free-inner-core nutation (FICN). We investigate this problem in the time domain and confirm the existence of the two modes. The periods of ICW and FICN are in good agreement with those obtained by other researchers. In studying the effects of coupling torques on the IC rotational modes we have found that depending on whether the IC net torque is 'restoring' or otherwise, an increased torque magnitude will respectively shorten or lengthen the ICW period. We have also found that the sense of FICN is determined by the orientation of the net coupling torque on the IC.     

Geographical and vertical variation of the earth's seismicity

Information concerning a total number of 13700 instrumentally recorded earthquakes is used to study the geographical and the vertical distribution of the Earth's seismicity. From these earthquakes, which form four complete samples of data (M 7.0, 1894–1992; M 6.5, 1930–1992; M 6.0, 1953–1992; M 5.5, 1966–1992), 11511 are shallow (h 60 km), 2085 are of intermediate focal depth (61 h 300 km) and 564 are deep focus earthquakes (301 h 720 km). The parameters a and b of the frequency-magnitude relationship were calculated in a grid of equally spaced points at 1° by using the data of earthquakes located inside circles centered at each point. The radius of the circles increased from 30 km with a step of 10 km until the information for the earthquakes located inside the circle fulfil three criteria which concern the size of the sample used to compute these parameters at each point of the grid. The results are given in a qualitative way (epicenter maps) as well as in a quantitative way (mean return periods).     

岩土工程数值模拟新方法

论述了岩土工程数值模拟的新进展和近年来新出现的数值模拟方法,重点介绍了无网络伽辽金法（ＥＦＧＭ）和数值流形法（ＭＭ）的原理及其在岩土工程中的应用,指出了今后研究的重点方向。     

THREE KINDS OF TIME DISTRIBUTION FUNCTIONS OF REMARKABLE EARTHQUAKES IN SEISMIC SEQUENCES

ＴＨＲＥＥＫＩＮＤＳＯＦＴＩＭＥＤＩＳＴＲＩＢＵＴＩＯＮＦＵＮＣＴＩＯＮＳＯＦＲＥＭＡＲＫＡＢＬＥＥＡＲＴＨＱＵＡＫＥＳＩＮＳＥＩＳＭＩＣＳＥＱＵＥＮＣＥＳＤｉａｏＳｈｏｕｚｈｏｎｇＷａｎｇＨｏｎｇｗｅｉＣｈａｏＨｏｎｇｔａｉＨｕａＡｉｊｕｎ（Ｓｅｉ...     

Explicit solution of a free boundary problem for a nonlinear absorption model of mixed saturated-unsaturated flow

In wet soils, zones of saturation naturally develop in the vicinity of impermeable strata, surface ponds and subterranean cavities. Hydrology must be then concerned with transient flow through coexisting unsaturated and saturated zones. The models of advancing saturated zones necessarily involve a nonlinear free boundary problem.A closed-form analytic solution is presented for a nonlinear diffusion model under conditions of ponding at the surface. The soil water diffusivity is restricted to the special functional form D(θ) = a/(b − θ)², where θ is the water content field to be determined and a, b are positive constants. The explicit solution depends on a parameter C (determined by the data of the problem), according to two cases: 1 < C < C₁ or C ≥ C₁, where C₁ is a constant which is obtained as the unique solution of an equation. This result complements the study given in P. Broadbridge, Water Resources Research, 1990, 26, 2435–2443, in order to established when the explicit solution is available. The behavior of the bifurcation parameter C₁ as a function of the driving potential is studied with the corresponding limits for small and large values. Moreover, the sorptivity is proven to be continuously differentiable function of the variable C.     

川西孔玉——会理金矿带同位素特征与金矿分布

金矿带内不同金矿床氢氧和硫同位素组成,清楚地反映出各金矿产出地质背景的差异,显示出金矿与赋矿围岩有成因联系;δ＾１８Ｏ石英和δ＾１８Ｏ水的变化趋势,反映出金矿空间分布规律及其成矿系列演化。     

Distribution of airborne pollen and spores and their long distance transport

The atmosphere near the ground contains a mixed population of pollen and spores in the 1 to 90 m diameter range. Continuous sampling at Rothamsted Experimental Station at 2 m above ground level indicated concentrations averaging 12,000 m^–3 over 5 summer months, but 1 million m^–3 can occur for short periods. Concentrations change rapidly with locality, season, time of day or night and weather. Normally concentration in the troposphere decreases logarithmically with height. The occurrence of long distance transport of pollen and spores by wind is demonstrated by sampling from aircraft, and supported by much circumstantial evidence. Possible effects of this air spora on the atmosphere may be sought in alterations to: opacity, ionization, condensation nuclei, and sinks for minor gases.     

Incursion of the Pacific Ocean Water into the Indian Ocean

Using the data collected during the International Indian Ocean Expedition, maps showing the distribution of depth, acceleration potential, salinity and oxyty were prepared for the northeast monsoon for the four potential thermosteric anomaly surfaces: 160, 120, 80 and 60 cl/t. Zonal components of current along 84°E were computed from the geopotential dynamic heights. From such an analysis, it became clear that low-salinity water from the Pacific intrudes into the western Indian Ocean through the Banda and Timor seas in the upper layers above 100 cl/t surface, while the North Indian Ocean Water penetrates towards the Eastern Archipelago below 100 cl/t surface. The South Equatorial Countercurrent and the Tropical Countercurrent are well depicted on the vertical section of zonal components as well as on the distribution of acceleration potential.